The linear alternating copolymers of carbon monoxide and aliphatic .alpha.-olefins are known in the art, being produced by the processes disclosed in U.S. Pat. No. 4,788,279 and copending U.S. patent application Ser. No. 352,235, filed May 15, 1989, now U.S. Pat. No. 4,965,341. The copolymers are produced according to these references in the presence of a catalyst composition formed from a palladium compound, the anion of a strong non-hydrohalogenic acid and a bidentate ligand of nitrogen or certain cyclic bidentate ligands of phosphorus. The polymers are broadly represented by the repeating formula EQU --CO--G-- (I)
wherein G represents the moiety of the aliphatic .alpha.-olefin of at least 3 carbon atoms. In terms of the fine structure of such polymers, they are termed regioregular and stereoregular.
The term "regioregular" refers to the manner in which moieties derived from the .alpha.-olefin are connected to the moieties derived from the carbon monoxide. If the .alpha.-olefin moieties are attached to the carbon monoxide moieties in predominantly, e.g., at least 50% of the time, a head-to-tail manner, the polymer is termed regioregular. A polymer with less than a predominance of head-to-tail bonding is termed regio-irregular or non-regioregular. The term stereoregular applies to the configuration of the asymmetric carbon atoms of the linear alternating polymer. When the configuration of adjacent asymmetric carbon atoms is the same, e.g., ##STR1## wherein R is alkyl and the wavy lines represent the continuing polymer chain, the configuration is termed syndiotactic and a polymer having a predominance of syndiotactic configurations, i.e., at least 50% of syndiotactic configurations, is considered to be a syndiotactic polymer. When the configuration of adjacent asymmetric carbon atoms is opposite, e.g., ##STR2## wherein R and the wavy line have the previously stated meaning, the configuration is termed isotactic and a polymer having a predominance of isotactic configurations is termed an isotactic polymer. Stereoregular polymers include those which are syndiotactic and those which are isotactic. A polymer in which there is no predominant or regular arrangement of adjacent asymmetric carbon atoms is termed atactic or stereo-irregular.
The production of linear alternating polymers of carbon monoxide and aliphatic .alpha.-olefin of at least 3 carbon atoms which are highly atactic is the subject of copending U.S. patent application Ser. No. 442,089, filed Nov. 28, 1989. However, the production of such linear alternating polymers which are highly stereoregular is not so easily accomplished. For some applications it is desirable to have a linear alternating polymer of carbon monoxide and aliphatic .alpha.-olefin of at least 3 carbon atoms which is entirely or predominantly atactic in character. For other applications it would be desirable to have such a linear alternating polymer high in stereoregular character, i.e., syndiotactic character or isotactic character. It would be of advantage to provide a method of obtaining a linear alternating polymer of carbon monoxide and aliphatic .alpha.-olefin of at least 3 carbon atoms of enhanced or greater stereoregular character.